JPH0814356B2 - Method and device for determining fastening state of pipe joint - Google Patents

Description

Description: [Industrial field of application] The present invention has a shoulder portion inside which a sealing action is made by contact with a pipe end surface, and for example, a screw-type pipe used for connecting oil well pipes. The present invention relates to a method for determining the quality of a joint and a device used for implementing the method.

[Conventional technology]

Pipe joints for oil well pipes used in the field of oil mining are required to have high sealing performance against high pressure in the pipes and sufficient strength to withstand the connection of a large number of pipes. Therefore, conventionally, a screw-in type pipe joint as shown in FIG. 4 configured to perform a sealing action by metal touch has been used.

The pipe joint 1 has female thread portions 10 and 10 each having a predetermined length from both ends.
Is a cylindrical member formed on the inner periphery thereof, and further on the inner side of the female threaded portions 10, 10, there are taper-shaped sealing surfaces 11 and 11 having a diameter reduced toward the inner portion, and the sealing surfaces. Shoulder surfaces 12, 12 which are continuous with 11, 11 and are substantially orthogonal to the axis of the pipe joint 1 are formed. On the other hand, the pipe 2 connected by the pipe joint 1
The end of the pipe has a seal end surface that is substantially orthogonal to the axis of the pipe 2.
22 and the seal surface 11 connected to the outer peripheral side of the seal end surface 22.
A tapered seal surface 21 corresponding to the above and a male thread portion 20 connected to the seal surface 21 and corresponding to the female thread portion 10 are formed. Thus, the pipe joint 1 and the pipe 2 are joined by fitting the end portion of the pipe 2 inside the pipe joint 1 and then rotating the pipe joint 1 around the axis so that the male screw portion 20 of the pipe 2 is formed. Female thread part 10 of pipe fitting 1
It is made by screwing. FIG. 5 is an enlarged sectional view of the fastening portion after the screwing. When the screws are properly screwed in as shown in the figure, the seal surface 11 on the inner circumference of the pipe joint 1 and the seal surface 21 on the outer circumference of the pipe 2 are in close contact with each other over the entire length to form a circumferential seal portion. Tube 2 on shoulder surface 12
The seal end surface 22 of the above is abutted and closely adhered to form a shoulder seal portion, and a high sealing performance can be obtained by the sealing action of both seal portions.

The fastening of the pipe 2 to the pipe joint 1 as described above is performed by a fastening machine that concentrically includes a rotary chuck that holds the pipe joint 1 and rotates about the axis, and a fixed chuck that holds the pipe 2 in a fixed manner. However, at this time, the tightening torque applied to the pipe joint 1 via the rotary chuck is detected, and the operation of the fastening machine is stopped immediately before the detection result reaches a predetermined upper limit torque to finish screwing, The pipe joint 1 and the pipe 2 are fastened under a tightening torque within a predetermined range close to the upper limit torque.

FIG. 6 is a graph showing a change state of the tightening torque applied to the pipe joint 1 during the operation of the fastening machine. The horizontal axis of this figure is the number of turns of the pipe joint 1, and when the tightening is correctly performed, the tightening torque gradually increases with an increase in the number of turns, and suddenly increases from the middle to the final tightening torque. The following is a change mode. The transition from the gradually increasing area to the rapidly increasing area is performed by connecting the shoulder surface 12 of the pipe joint 1 to the seal end surface 22 of the pipe 2.
Occurs at the time when is hit. That is, the tightening torque applied to the pipe joint 1 is between the female screw portion 10 and the male screw portion 20 and between the seal portion 11 and the seal portion in the gradually increasing region.
This is because it is consumed exclusively in order to resist the frictional resistance between it and 21, while it is mainly consumed in the rapid increase area due to the pressing of the shoulder surface 12 against the seal end surface 22. Therefore, whether or not the coordinates of the inflection point A from the gradually increasing region to the rapidly increasing region are proper, specifically, whether the number of turns and the tightening torque at the inflection point A are within proper ranges, respectively. By checking, it is possible to judge the quality of the tightened state. For example, in the tightening process, the female screw portion 10
When seizure occurs between the male screw portion 20 and the male screw portion 20, as a result of a sharp increase in the tightening torque at the time of the seizing, a change mode as shown by the broken line in the figure is obtained, and the female screw portion 10 and the male screw portion 20 are If the tightening margin between the seal portion 11 and the seal portion 21 is larger than the appropriate value, the friction resistance is large and the inclination in the gradually increasing region is large, and the change shown by the dashed line in the figure Aspects are obtained. All of these reach the final tightening torque before reaching the predetermined number of turns, and the fastening is completed when the contact between the shoulder surface 12 and the seal end surface 22 does not occur or the contact is insufficient,
Although the desired sealing performance is not obtained, as shown in the figure, the inflection point is generated at a position greatly different from the regular inflection point A, so that it is determined that the fastening is defective. There is no risk that the pipe joint 1 that has been fastened will be used as it is.

[Problems to be Solved by the Invention]

Now, in order to judge the fastening state of the pipe joint as described above, generally, the tightening torque and the number of turns during fastening are continuously detected by the torque detector and the turn detector mounted on the rotary chuck of the fastening machine. , These detection results are output in the form of a graph or a number table, and the judgment is made by the operator who visually recognizes this output display, but it requires a dedicated operator and goes against the demand for labor saving. As a result, it is inevitable that there will be individual differences among workers.

Therefore, in order to realize labor saving by automating the determination, in JP-A-63-229272, the detection results of the torque detector and the turn detector are sampled at a minute time interval from the start of fastening, The difference between each sampling torque and the previous sampling torque is calculated in real time, and the inflection point A is extracted when this difference exceeds a preset reference value, and the tightening torque and the number of turns at this time are extracted. There has been proposed a method for judging whether the fastening state is good or not depending on whether or not is within an appropriate range. However, in the gradual increase area before the inflection point A, there are various disturbance factors that cause fluctuations in the tightening torque, such as foreign matter being caught in the threaded portion between the female screw portion 10 and the male screw portion 20. Since the tightening torque of No. 1 fluctuates as shown in FIG. 6, when the above-mentioned method is adopted, the local sharp increase portion in the gradually increasing region has an inflection point A.
Therefore, there is a possibility that the quality of the fastening state may be erroneously determined based on the extraction result, and the reliability of the determination result is extremely low.

The present invention has been made in view of such circumstances, a determination method that can reliably and automatically determine the quality of the fastening state of the pipe joint, and can reduce the labor of the determination work with high reliability, and an implementation thereof. The object is to provide a device for use in.

[Means for solving the problem]

The method for determining the fastening state of a pipe joint according to the present invention is such that when a pipe joint having a shoulder surface that performs a sealing action by contact with a pipe end surface is screwed into a pipe at a predetermined tightening torque and is fastened, In the method of determining the inflection point of the tightening torque generated by the contact between the end face and the shoulder surface, the tightening torque at the inflection point and the number of turns of the pipe joint are used to determine the quality of the tightening, the tightening torque and The number of turns is sampled at every predetermined time and sequentially stored in association with each other, and the number of turns in the stored data is within the range between the final number of turns at the end of the fastening and the number of turns smaller by a predetermined number. Differences per turn are calculated for tightening torques corresponding to several numbers, and the maximum value among the obtained difference values is multiplied by a predetermined coefficient to determine the reference value of the difference value. , Comparing the difference value obtained from the tightening torque and the number of turns in the reverse order of storage with the reference value, first extracting the difference value below the reference value, and tightening torque of the stored data corresponding thereto and The number of turns is the tightening torque and the number of turns at the inflection point.

A fastening state determination device for a pipe joint according to the present invention is a fastening machine for screwing and fastening a pipe joint having a shoulder surface, which has a sealing function inside by contact with a pipe end surface, into a pipe, and a tightening torque and a turn of the pipe joint. A torque detector and a turn detector for respectively detecting the numbers, and when the detected torque of the torque detector reaches a predetermined value, the fastening machine is stopped to finish screwing, and the torque detector and the turn detector during this period are detected. The inflection point of the tightening torque generated by the contact between the shoulder surface and the pipe end surface based on the detection result of the vessel,
In the fastening state determination device of the pipe joint that determines the quality of the fastening based on the tightening torque and the number of turns at this inflection point, the detection results of the torque detector and the turn detector are displayed until the end of the screwing. A sampling storage unit that samples at predetermined time intervals and sequentially stores them in correspondence with each other, and the storage data of the sampling storage unit is collectively read after the screwing is completed, and each is traced back from the final storage data corresponding to the end time. A difference calculation unit that calculates a difference value per turn for each tightening torque, a maximum value among the difference values, and a reference value setting unit that determines a reference value of the difference value by multiplying it by a predetermined coefficient,
This reference value is compared with each difference value obtained in the reverse order of the tightening torque and the number of turns stored in the storage unit, and the tightening torque of the stored data corresponding to the difference value that first falls below the reference value and An inflection point extraction unit that extracts the number of turns as the tightening torque and the number of turns at the inflection point is provided.

[Action]

In the present invention, from the start to the end of screwing the pipe joint into the pipe, the tightening torque and the number of turns applied to the pipe joint are sampled and stored at predetermined intervals,
After the fastening is completed, the stored data is read out, the difference between each stored data is calculated within the range of the number of turns which is smaller than the number of turns at the end by a predetermined number to obtain the change rate of the tightening torque, and then the maximum difference value is set to the predetermined value. A reference value serving as the extraction reference of the inflection point is determined by multiplying the coefficient, and the reference value and the previously obtained difference value are reversed from the order of the memory, that is, from the one corresponding to the screwing end time to the sampling time. And the stored data corresponding to the difference value that first fell below the reference value by this comparison as the tightening torque and the number of turns at the inflection point, and fastened depending on whether these are within a predetermined range. The quality of the state is determined.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing an embodiment thereof. FIG. 1 is a schematic block diagram showing an embodiment of a method for determining a fastening state of a pipe joint according to the present invention (hereinafter referred to as a method of the present invention).

In the figure, 1 is a pipe joint, and 2 is a pipe connected by the pipe joint 1, and each of them has the structure as described above. The pipe joint 1 and the pipe 2 are mounted on a fastening machine 3 including a fixed chuck 30 and a rotary chuck 31 which are concentrically arranged side by side, and are automatically fastened by the operation of the fastening machine 3. That is, the fastener 3 firmly grips the pipe joint 1 on the rotary chuck 31 and the fixed chuck 30 near the end of the pipe 2, positions the both coaxially, and then drives the drive motor 32. The rotary chuck 31 is rotated to bring the pipe joint 1 closer to the pipe 2 while rotating the pipe joint 1 around the axis, whereby the female screw portion 10 (see FIG. 4) formed on the inner circumference of the pipe joint 1 is piped. The pipe joint 1 is fastened to the pipe 2 by being screwed into the male screw portion 20 formed on the outer periphery of the end portion of 2. At this time, the tightening torque applied to the pipe joint 1 and the cumulative number of revolutions (turns) of the pipe joint 1 from the start of fastening are determined by the torque detector 33 attached to the fixed chuck 30 and the rotary chuck 31. The torque detected by the torque detector 33 is detected by the turn detector 34 and the torque detected by the torque detector 33. The fastening control unit 4 controls the fastening operation of the fastening machine 3.
And the detection torque and turn detection unit
The number of turns detected at 34 is given to the fastening state determiner 5 which determines the quality of the fastening state according to the method of the present invention.

The fastening control section 4 uses the torque detected by the torque detector 33 as a feedback signal to perform an operation of issuing a drive command to the drive control section 6, and the drive motor 32 of the rotary chuck 31 is operated by the operation of the drive control section 6 according to this drive command. As a result of the adjustment of the drive current to the pipe fitting 1, a sufficient tightening torque to resist the resistance at the time of screwing is given to the pipe fitting 1, and
Signing to Then, the fastening control unit 4 stops the output of the drive command to the drive control unit 6 immediately before the detected torque given from the torque detector 33 reaches a preset upper limit torque, and the drive control unit 6 according to this stop stops. By the operation, the power supply to the drive motor 32 is cut off, and the screwing of the pipe joint 1 into the pipe 2 is completed. With the above operation, the pipe joint 1 and the pipe 2 are fastened together with the final tightening torque close to the upper limit torque.

The drive command issued by the fastening control unit 4 is also given to the fastening state determiner 5, and the fastening state determiner 5 determines whether the fastening state is good or not according to the drive command as described later.

As shown in the figure, the fastening state determiner 5 includes a sampling storage unit.
50, a difference calculation unit 51, a reference value setting unit 52, an inflection point extraction unit 53, and a determination unit 54, the drive signal generated by the fastening control unit 4 is given to the sampling storage unit 50 and the difference calculation unit 51. Further, the detection signals of the torque detector 33 and the turn detector 34 are given to the sampling storage unit 50. The sampling storage unit 50 is detected by the torque detector 33 and the turn detector 34, respectively, while the drive signal from the fastening control unit 4 is being given, in other words, while the fastening operation by the fastening machine 3 is being performed. The tightening torque and the number of turns are sampled at predetermined intervals, and these are stored in correspondence with each other. In addition, the sampling interval at this time can be freely changed by manual setting to the sampling interval setting device 7 provided externally, and the sampling interval in the sampling storage unit 50 is the length of the screwing length,
It is appropriately set according to the fastening conditions such as the required determination accuracy. As a result of the above operation, for example, when the sampling is performed n times before the completion of the fastening, the sampling storage unit 50 puts a circle mark on the graph of FIG. 2 showing the changing state of the fastening torque. A set of tightening torque and the detected value of the number of turns obtained at each sampling time is stored in n sets.

The difference calculation unit 51 starts the operation as soon as the drive command from the fastening control unit 4 is stopped, that is, the fastening operation by the fastening machine 3 is finished, and first, the n sets of stored data stored in the sampling storage unit 50 are collectively collected. Data is read out and the set of stored data satisfying the condition that the difference from the number of turns N _n in the n-th set of stored data obtained immediately before the fastening is smaller than the predetermined value α is extracted. As shown in FIG. 2, for example, when the above conditions are satisfied in the stored data up to the m-th group, that is, when N _n −N _m <α, the (n-th) -M + 1) sets of stored data are extracted, and the subsequent processing is performed only for these.
In addition, the predetermined value α is, on the graph showing the change mode of the tightening torque expected when proper tightening is made,
Since the inflection point A between the gradually increasing region and the rapidly increasing region of the tightening torque is set in advance so as to be sufficiently included in the extraction range, the subsequent processing is performed as a whole of the rapidly increasing region and a part of the gradually increasing region. It is carried out within the range including. After extracting the processed data as described above, the difference calculation unit 51 determines the difference value X _i for each of these.
Is calculated by the following equation.

The difference value X _i calculated in this way corresponds to the change rate of the tightening torque at the i-th sampling time point, and these are given to the reference value setting unit 52 and the inflection point extraction unit 53.
In the reference value setting unit 52, the maximum value X _max in the (nm) pieces of difference data X _i given from the difference calculation unit 51, that is, the maximum value of the tightening torque change rate within the above-mentioned processing range is set. The obtained value is then multiplied by a predetermined coefficient set in advance to set a reference value X as an extraction reference of the inflection point A, and this result is given to the inflection point extraction unit 53. The coefficient is a constant that is empirically determined based on many fastening results, and varies depending on the fastening conditions such as the type of pipe fitting 1, the inner diameter, and the like. FIG. 3 is a graph showing an example in which the difference value X _i calculated by the equation (1) is plotted against the corresponding number of turns. As shown in the figure, the difference value X _i generally increases rapidly with the entry into the rapid increase region, and immediately before the end of tightening, the drive current to the drive motor 32 is gradually reduced in preparation for the stop of the fastening machine 3. Therefore, it shows a slight decrease. In this case, the maximum value X
It goes without saying that _max and the reference value X are respectively determined as shown in the drawing, and X _max exists in the rapid increase area.

Now, in the inflection point extraction unit 53, the difference data within the processing range given from the difference calculation unit 51 and the reference value setting unit
The comparison with the reference value X set at 52 is performed in the reverse order of the storage in the sampling storage unit 50, that is, from X _n corresponding to the final storage data, and the difference that is first lower than the reference value X is obtained. A value is extracted, the storage data corresponding to this difference value is read from the difference calculation unit 51, and this storage data is given to the determination unit 54 as corresponding to the inflection point A. For example, when the difference data shown in FIG. 3 is obtained, the inflection point extraction unit 53
In, the number of turns N _x corresponding to the difference value that first falls below the reference value X is first determined, and the tightening torque T _x corresponding to this number of turns N _x is determined as shown in FIG.
These are given to the determination unit 54 as the number of turns and the tightening torque at the inflection point A. When the tightening torque and the number of turns are each within a predetermined proper range, the determination unit 54 determines that good fastening is performed, and if the fastening torque is not within the proper range, determines that the fastening is defective. The result is given to the display unit 8 and the operation for displaying the result on the display unit 8 is performed. It should be noted that as shown in FIG.
The stored data may be also given, and all the stored data may be displayed together with the determination result of the determination unit 54.

〔effect〕

As described above in detail, in the method of the present invention and the apparatus of the present invention, the tightening torque and the number of turns during screwing of the pipe joint into the pipe are stored, and after the fastening is completed, this stored data is used as the starting point at the fastening end point. The difference value of the torque per turn is checked in the order of increasing and decreasing gradually, and the point where the tightening difference value is below the reference value is used as the tightening torque and the number of turns at the inflection point. The work efficiency is high, and it is possible to avoid the influence of the torque fluctuation due to the disturbance on the way, and it is possible to obtain the excellent effect that the determination can be performed with high reliability.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an implementation state of the method of the present invention, FIG. 2 is an explanatory diagram of a sampling aspect of tightening torque and number of turns, and FIG. 3 is a graph showing an example of a difference result,
FIG. 4 is a sectional view of a pipe joint and a pipe to which the method of the present invention is applied,
FIG. 5 is an enlarged cross-sectional view of the joint between the pipe joint and the pipe, and FIG. 6 is a graph showing various changes in the tightening torque applied to the pipe joint when the pipe is fastened. 1 ... Pipe joint, 2 ... Pipe, 3 ... Fastening machine, 5 ... Fastening state determiner, 12 ... Shoulder surface, 22 ... Seal end surface, 33 ...
… Torque detector, 34 …… Turn detector, 50 …… Sampling storage unit, 51 …… Difference calculation unit, 52 …… Reference value setting unit,
53 ... inflection extraction section, 54 ... determination section, A ... inflection point

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-229272 (JP, A) JP-A-61-182781 (JP, A) JP-A-3-54430 (JP, A)

Claims (2)

[Claims] 1. When a pipe joint having a shoulder surface inside which a sealing action is made by contact with a pipe end face is screwed into a pipe with a predetermined tightening torque and fastened, the end face of the pipe contacts the shoulder face. In the method of determining the inflection point of the tightening torque generated by, and determining the quality of the fastening by the tightening torque at this inflection point and the number of turns of the pipe joint, sampling the tightening torque and the number of turns every predetermined time. Then, the tightening torques are sequentially stored in correspondence with each other, and the tightening torques corresponding to the respective turn numbers in the stored data within the range between the final turn number at the end of the fastening and the turn number smaller than the final turn number by a predetermined number. The difference calculation for each turn is performed, and the maximum value among the obtained difference values is multiplied by a predetermined coefficient to determine the reference value of the difference value. The difference value obtained from these values is compared with the reference value in the reverse order of the memory number storage, and the difference value below the reference value is first taken out. A method for determining a fastening state of a pipe joint, which comprises setting a fastening torque and a number of turns at a bending point. 2. A fastener machine for screwing and fastening a pipe joint having a shoulder surface, which has a sealing surface inside by contact with the pipe end face, into the pipe, and a torque detector for detecting the tightening torque and the number of turns of the pipe joint, respectively. And a turn detector, and when the detected torque of the torque detector reaches a predetermined value, the fastening machine is stopped and screwing is completed, and the torque detector and the turn detector detect the torque based on the detection result during this period. In a fastening state determination device for a pipe joint, which determines an inflection point of a tightening torque generated by contact between a shoulder surface and the pipe end surface, and determines the quality of the fastening by the tightening torque and the number of turns at the inflection point, Sampling in which the detection results of the torque detector and the turn detector are sampled at predetermined time intervals until the completion of screwing, and are sequentially stored in association with each other. A storage unit and a difference calculation unit that collectively reads the storage data of the sampling storage unit after the screwing is completed and that calculates the difference value per turn for each tightening torque by tracing back from the final storage data corresponding to the end time. A reference value setting unit for extracting a maximum value from the difference values and multiplying the maximum value by a predetermined coefficient to set a reference value for the difference value; and storing the reference value and the tightening torque and the number of turns in the storage unit. The difference values obtained in the order and the reverse order are compared, and the tightening torque and the number of turns of the stored data corresponding to the difference value that first falls below the reference value are extracted as the tightening torque and the number of turns at the inflection point. And an inflection point extracting section for controlling the inflection point of the pipe joint.